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4–3 Second PID Set

In certain applications the character-

istics of a process are strongly relat-

ed to its process value. The TEC-

9300 provides two sets of PID val-

ues. When the process is changed to

a different set point, the PID values

can be switched to another set to

achieve optimum conditions.

Auto-tuning second PID

The optimal PID values for a

process may vary with its process

value and set point. Hence if a

process is used for a wide range of

set points, dual PID values are necessary to optimize control per-

formance. If the first PID set is selected (event input is not

applied) during auto-tuning procedure, the PID values will be

stored in PB1, TI1, and TD1. Similarly, if the second PID set is

selected (event input is applied while PID2 or SP.P2 is selected

for EIFN) during auto-tuning, the PID values will be stored in

PB2, TI2, and TD2 as soon as auto-tuning is completed.

Application 1: programmed by the set point

Choose SP.P2 for EIFN then both set point and PID values will

be switched to another set simultaneously.

The signal applied to the event input may

come from a timer, a PLC, an alarm relay, a

manual switch or other devices.

Application 2: programmed by

the process value

If the process value exceeds a certain limit,

500°C for example, it is desirable to use

another set of PID values to optimize con-

trol performance. You can use a process

high alarm to detect the limit of the process

value. Choose PV1H for A1FN, NORM for

A1MD, adjust A1SP to be equal to 500°C,

and choose PID2 for EIFN. If the tempera-

ture is higher than 500°C, then alarm 1 is activated. The alarm 1

output is connected to the event input, so the PID values will

change from PB1, TI1, and TD1 to PB2, TI2, and TD2.

Refer to section 5-9 for more details.

EIFN=SP.P2

EIFN=PID2

Alarm output

controls the

event input

Apply

Signal To

Event input +

Event input –

Setup

EIFN choose PID2 or

SP.P2

4–4 Ramp and Dwell

Ramp

The ramping function is performed

during power up as well as any

time the set point is changed.

Choose MINR or HRR for SPMD,

and the unit will perform the ramp-

ing function. The ramp rate is pro-

grammed by using RAMP, which

is found in the user menu.

Example without dwell timer

Select MINR for SPMD, °C for IN1U, 1-DP for DP1, and set

RAMP=10.0. SP1 is set to 200°C initially, then changed to 100°C

30 minutes after power up. The starting temperature is 30°C.

After power up, the process runs like the curve shown below:

Note: When the ramp function is used, the lower display will

show the current ramping value. However, it will revert to show

the set point value as soon as the up or down key is pressed for

adjustment. The ramping value is initiated as the process value

either at power up or when RAMP and/or the set point are

changed. Setting RAMP to zero means no ramp function at all.

Dwell

The dwell timer can be used

separately or in conjunction

with a ramp. If A1FN is set for

TIMR, alarm 1 will act as a

dwell timer. Similarly, alarm 2

will act as a dwell timer if A2FN is set for TIMR. The timer is

programmed by using TIME which is in the user menu. The timer

starts to count as soon as the process reaches its set point, and

triggers an alarm when it times out. Here is an example.

Example without ramp

Select TIMR for A1FN, °F for IN1U, NODP for DP1, and set

TIME=30.0. SP1 is set to 400°F initially, and corrected to 200°F

before the process reaches 200°F. When the process reaches the

set point (i.e., 200°F), the timer starts to count. The TIME value

can still be corrected without disturbing the timer before time out.

Example: TIME is changed to 40.0, 28 minutes after the process

has reached its set point. The behavior of the process value and

alarm 1 are shown below.

Once the timer output is energized, it will remain unchanged

until power down or an event input programmed for resetting

the alarm is applied.

Note: TIMR can’t be chosen for A1FN and A2FN simultaneous-

ly, or an error code will result.

4–4 Ramp and Dwell, continued next page…

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